Interference and ion effects in the electro-optical response of PDNLC films

We have considered the interference in polymer-dispersed nematic liquid-crystal (PDNLC) films caused by the superposition of light beams that pass through and between the LC droplets. The relative phase retardation of the beams depends on the applied voltage, and, as a consequence, interference oscillations can occur at transmittance-voltage curves. Typical forms of the curves for composite films with various structures are presented. Interference oscillations were revealed not only in the static electro-optical characteristics but in the dynamic ones also. For PDLC films based on commercially available components produced without thorough purification, the combination of interference and ionic effects is observed in the dynamics of the optical response. The relaxation of transmittance due to the depolarization ionic field is presented, depending on droplet size, temperature, pulse duration, and the concentration of the ionic admixture.